RESUMEN
The mechanisms of cellular energy sensing and AMPK-mediated mTORC1 inhibition are not fully delineated. Here, we discover that RIPK1 promotes mTORC1 inhibition during energetic stress. RIPK1 is involved in mediating the interaction between AMPK and TSC2 and facilitate TSC2 phosphorylation at Ser1387. RIPK1 loss results in a high basal mTORC1 activity that drives defective lysosomes in cells and mice, leading to accumulation of RIPK3 and CASP8 and sensitization to cell death. RIPK1-deficient cells are unable to cope with energetic stress and are vulnerable to low glucose levels and metformin. Inhibition of mTORC1 rescues the lysosomal defects and vulnerability to energetic stress and prolongs the survival of RIPK1-deficient neonatal mice. Thus, RIPK1 plays an important role in the cellular response to low energy levels and mediates AMPK-mTORC1 signaling. These findings shed light on the regulation of mTORC1 during energetic stress and unveil a point of crosstalk between pro-survival and pro-death pathways.
Asunto(s)
Proteína 5 Relacionada con la Autofagia/genética , Proteína de Dominio de Muerte Asociada a Fas/genética , Intestino Grueso/metabolismo , Diana Mecanicista del Complejo 1 de la Rapamicina/genética , Proteína Serina-Treonina Quinasas de Interacción con Receptores/genética , Proteínas Quinasas Activadas por AMP/genética , Proteínas Quinasas Activadas por AMP/metabolismo , Animales , Animales Recién Nacidos , Proteína 5 Relacionada con la Autofagia/deficiencia , Caspasa 8/genética , Caspasa 8/metabolismo , Muerte Celular/genética , Proteína de Dominio de Muerte Asociada a Fas/deficiencia , Regulación de la Expresión Génica , Glucosa/antagonistas & inhibidores , Glucosa/farmacología , Células HEK293 , Células HT29 , Humanos , Intestino Grueso/efectos de los fármacos , Intestino Grueso/patología , Células Jurkat , Lisosomas/efectos de los fármacos , Lisosomas/metabolismo , Lisosomas/patología , Diana Mecanicista del Complejo 1 de la Rapamicina/metabolismo , Metformina/antagonistas & inhibidores , Metformina/farmacología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Fosforilación , Proteína Serina-Treonina Quinasas de Interacción con Receptores/deficiencia , Transducción de Señal , Sirolimus/farmacología , Proteína 2 del Complejo de la Esclerosis Tuberosa/genética , Proteína 2 del Complejo de la Esclerosis Tuberosa/metabolismoRESUMEN
Necroptosis, a cell death pathway mediated by the RIPK1-RIPK3-MLKL signaling cascade downstream of tumor necrosis factor α (TNF-α), has been implicated in many inflammatory diseases. Members of the TAM (Tyro3, Axl, and Mer) family of receptor tyrosine kinases are known for their anti-apoptotic, oncogenic, and anti-inflammatory roles. Here, we identify an unexpected role of TAM kinases as promoters of necroptosis, a pro-inflammatory necrotic cell death. Pharmacologic or genetic targeting of TAM kinases results in a potent inhibition of necroptotic death in various cellular models. We identify phosphorylation of MLKL Tyr376 as a direct point of input from TAM kinases into the necroptosis signaling. The oligomerization of MLKL, but not its membranal translocation or phosphorylation by RIPK3, is controlled by TAM kinases. Importantly, both knockout and inhibition of TAM kinases protect mice from systemic inflammatory response syndrome. In conclusion, this study discovers that immunosuppressant TAM kinases are promoters of pro-inflammatory necroptosis, shedding light on the biological complexity of the regulation of inflammation.
Asunto(s)
Proteínas Quinasas/genética , Proteínas Proto-Oncogénicas/genética , Proteínas Tirosina Quinasas Receptoras/genética , Síndrome de Respuesta Inflamatoria Sistémica/genética , Tirosina Quinasa c-Mer/genética , Animales , Apoptosis/genética , Células HEK293 , Humanos , Ratones , Ratones Noqueados , Necroptosis/genética , Fosforilación , Proteína Serina-Treonina Quinasas de Interacción con Receptores/genética , Síndrome de Respuesta Inflamatoria Sistémica/patología , Factor de Necrosis Tumoral alfa/genética , Tirosina Quinasa del Receptor AxlRESUMEN
Necroptosis is a lytic programmed cell death mediated by the RIPK1-RIPK3-MLKL pathway. The loss of Receptor-interacting serine/threonine-protein kinase 3 (RIPK3) expression and necroptotic potential have been previously reported in several cancer cell lines; however, the extent of this loss across cancer types, as well as its mutational drivers, were unknown. Here, we show that RIPK3 expression loss occurs progressively during tumor growth both in patient tumor biopsies and tumor xenograft models. Using a cell-based necroptosis sensitivity screen of 941 cancer cell lines, we find that escape from necroptosis is prevalent across cancer types, with an incidence rate of 83%. Genome-wide bioinformatics analysis of this differential necroptosis sensitivity data in the context of differential gene expression and mutation data across the cell lines identified various factors that correlate with resistance to necroptosis and loss of RIPK3 expression, including oncogenes BRAF and AXL. Inhibition of these oncogenes can rescue the RIPK3 expression loss and regain of necroptosis sensitivity. This genome-wide analysis also identifies that the loss of RIPK3 expression is the primary factor correlating with escape from necroptosis. Thus, we conclude that necroptosis resistance of cancer cells is common and is oncogene driven, suggesting that escape from necroptosis could be a potential hallmark of cancer, similar to escape from apoptosis.